Three different particle sizes from cadmium telluride semiconductor quantum dots (CdTe QDs)
have been prepared using thioglycolic acid as a capping agent in aqueous media. The photophysical behavior
for these particles has been studied in presence of monomethine dyes belong to thiazole orange (TO) family.
The aggregation of the cyanine dyes on QDs surface was attributed to the presence of electrostatic attraction
between negatively charged thioglycolic capping molecules and the ionic dye. Energy transfer process from
CdTe QDs to cyanine dyes was also studied using electronic absorption and steady state emission
measurements. The energy transfer parameters such as Stern- Volmer rate constants Ksv, binding sites n,
quenching sphere radius "r", critical energy transfer distance "R0" and the efficiency of energy transfer E, have
been calculated. The enhancement in the triplet state emission and absorption for the studied dye in the
presence of QDs was expected to play a role in molecular oxygen sensitization and photodynamic therapy
(PDT) as well as photovoltaic applications.